Polyacrylamide gel electrophoresis (PAGE) is one of the most effective methods known for the analytical separation of proteins and peptides. However, the preparative procedure of PAGE, which should permit the separation of larger quantities of substances into their mixture components is often made difficult by technical problems. Using a gel layer which is approximately 3 mm thick, the widely used slab gel electrophoresis process permits substance charges up to 13 mg of protein per square centimeter, but the separating resolution is inferior, this being an inherent problem of slab gel electrophoresis due to the unavoidable boundary effects. In general, equipment used for slab gel electrophoresis, which is generally preferred for analytical purposes, has at best a semipreparative capacity with regard to the material density and quantity to be transported.
An apparatus for preparative column electrophoresis is known, for example, from U.S. Pat. No. 3,375,187, Buchler. This patent discloses a system in which the separation of substance mixtures is accomplished in a hollow cylindrical gel column which is introduced between an outer cylinder with a cooling jacket and an inner cooled probe or cold finger. The gel column in this apparatus is mounted in an electrical field, and the electrophoretical separation of peptide material usually proceeds according to plan until the beginning of elution of the material to be separated. When elution of the mixture components begins, there is a tendency for the separated substance bands to successively and asymmetrically "run into" the elution which, in the case of geometrically close separation, leads to partial mixing. In other words, the separated substances are mixed together when there is limited spacing between bands. The apparatus also has a tendency toward incomplete elution and attempts have been made to remove this deficiency by increasing the liquid flow. The resulting undesired dilution of the samples has the effect of preventing the detection of certain substances. For example, continuous UV detection in the range around 280 nm of peptide material is disturbed to the extent that the measurement becomes unusable. The elution liquid also is subject to bubbling, but a debubbler associated with that system helps to combat this problem. It is also disadvantageous that the cooling in the lower column section reserved for elution is not adequate for a number of separating problems. In addition, manipulation with the described apparatus is very complicated, particularly if a gradient gel is to be poured.